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pksunkara/pgx_ulid(opens in a new tab)
Language: Rust
Postgres extension for ulid
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- Last updated
- 02/23/2026
gem-hunterLanguage: Rust
Postgres extension for ulid
A postgres extension to support ulid.
There are several different postgres extensions for ulid, but all of them have feature gaps. A good extension should have:
ulid which is displayed as ulid text.| Name | Language | Generator | Binary | Type | UUID | Timestamp | Monotonic |
|---|---|---|---|---|---|---|---|
pgx_ulid |
Rust | ✔️ | ✔️ | ✔️ | ✔️ | ✔️ | ✔️ |
pgulid |
PL/pgSQL | ✔️ | ❌ | ❌ | ❌ | ❌ | ❌ |
pg_idkit |
Rust | ✔️ | ❌ | ❌ | ❌ | ❌ | ❌ |
uids-postgres |
Rust | ✔️ | ⁉️1 | ❌ | ⁉️2 | ❌ | ❌ |
pgsql_ulid |
PL/pgSQL | ❌ | ⁉️1 | ❌ | ✔️ | ❌ | ❌ |
pg-ulid |
C | ✔️ | ❌ | ❌ | ❌ | ❌ | ❌ |
ulid-postgres |
PL/pgSQL | ✔️ | ❌ | ✔️ | ❌ | ✔️ | ❌ |
pg_ulid |
Go | ✔️ | ❌ | ❌ | ❌ | ✔️ | ❌ |
pg_ulid |
C++ | ✔️ | ⁉️1 | ❌ | ✔️ | ❌ | ❌ |
The main advantages are:
This extension is approximately 30% faster than both pgcrypto's UUID and pg_uuidv7's UUIDv7 when generating a million identifiers.
ulid=# EXPLAIN ANALYSE SELECT gen_random_uuid() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=16) (actual time=46.630..1401.638 rows=1000000 loops=1)
Planning Time: 0.020 ms
Execution Time: 1430.364 ms
(3 rows)
ulid=# EXPLAIN ANALYSE SELECT uuid_generate_v7() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=16) (actual time=46.977..1427.477 rows=1000000 loops=1)
Planning Time: 0.031 ms
Execution Time: 1456.333 ms
(3 rows)
ulid=# EXPLAIN ANALYSE SELECT gen_ulid() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=32) (actual time=46.820..1070.447 rows=1000000 loops=1)
Planning Time: 0.020 ms
Execution Time: 1098.086 ms
(3 rows)
This extension is approximately 20% faster than both pgcrypto's UUID and pg_uuidv7's UUIDv7 when generating and inserting a million identifiers.
ulid=# EXPLAIN ANALYSE INSERT INTO uuid_keys(id) SELECT gen_random_uuid() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------
Insert on uuid_keys (cost=0.00..22500.00 rows=0 width=0) (actual time=2006.633..2006.634 rows=0 loops=1)
-> Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=16) (actual time=46.846..1459.869 rows=1000000 loops=1)
Planning Time: 0.029 ms
Execution Time: 2008.195 ms
(4 rows)
ulid=# EXPLAIN ANALYSE INSERT INTO uuid7_keys(id) SELECT uuid_generate_v7() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------
Insert on uuid7_keys (cost=0.00..22500.00 rows=0 width=0) (actual time=2030.731..2030.731 rows=0 loops=1)
-> Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=16) (actual time=46.894..1479.223 rows=1000000 loops=1)
Planning Time: 0.030 ms
Execution Time: 2032.296 ms
(4 rows)
ulid=# EXPLAIN ANALYSE INSERT INTO ulid_keys(id) SELECT gen_ulid() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------
Insert on ulid_keys (cost=0.00..22500.00 rows=0 width=0) (actual time=1665.380..1665.380 rows=0 loops=1)
-> Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=32) (actual time=46.719..1140.979 rows=1000000 loops=1)
Planning Time: 0.029 ms
Execution Time: 1666.867 ms
(4 rows)
This extension supports monotonicity through gen_monotonic_ulid() function. To achive this, it uses PostgreSQL's shared memory and LWLock to store last generated ULID.
To be able to use monotonic ULID's, it is necessary to add this extension to postgresql.conf's shared_preload_libraries configuration setting.
shared_preload_libraries = 'pgx_ulid' # (change requires restart)
ulid=# EXPLAIN ANALYSE SELECT gen_ulid() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=32) (actual time=47.207..2908.978 rows=1000000 loops=1)
Planning Time: 0.035 ms
Execution Time: 4053.482 ms
(3 rows)
ulid=# EXPLAIN ANALYSE SELECT gen_monotonic_ulid() FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=32) (actual time=46.479..2586.654 rows=1000000 loops=1)
Planning Time: 0.037 ms
Execution Time: 3693.901 ms
(3 rows)
ulid=# EXPLAIN ANALYZE INSERT INTO users (name) SELECT 'Client 1' FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------
Insert on users (cost=0.00..12500.00 rows=0 width=0) (actual time=8418.257..8418.261 rows=0 loops=1)
-> Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=64) (actual time=99.804..3013.333 rows=1000000 loops=1)
Planning Time: 0.066 ms
Execution Time: 8419.571 ms
(4 rows)
ulid=# EXPLAIN ANALYZE INSERT INTO users (name) SELECT 'Client 2' FROM generate_series(1, 1000000);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------
Insert on users (cost=0.00..12500.00 rows=0 width=0) (actual time=8359.558..8359.561 rows=0 loops=1)
-> Function Scan on generate_series (cost=0.00..12500.00 rows=1000000 width=64) (actual time=64.449..2976.754 rows=1000000 loops=1)
Planning Time: 0.090 ms
Execution Time: 8360.840 ms
(4 rows)
gen_ulid() when generating lots of ULIDs within one millisecond. Because, in this case, there is no need to generate random component of ULID. Instead it is just incremented.Previously generated ULID is saved in shmem and accessed via LWLock. i.e. it is exclusive for function invocation within database. Theoretically this can lead to slowdowns.
...But, in practice (at least in our testing) gen_monotonic_ulid() is slightly faster than gen_ulid().
Extensions that use shared memory must be loaded via postgresql.conf's shared_preload_libraries configuration setting.
...But, it only affects gen_monotonic_ulid() function. Other functions of this extension will work normally even without this config.
Monotonic ULIDs may overflow and throw an error.
...But, chances are negligible.
Use the extension in the database:
CREATE EXTENSION ulid;
-- or try "CREATE EXTENSION pgx_ulid;" if installed manuallyCreate a table with ulid as a primary key:
CREATE TABLE users ( id ulid NOT NULL DEFAULT gen_ulid() PRIMARY KEY, name text NOT NULL );
Or, create a table with monotonic ulid as a primary key:
CREATE TABLE users ( id ulid NOT NULL DEFAULT gen_monotonic_ulid() PRIMARY KEY, name text NOT NULL );
Operate it normally with text in queries:
SELECT * FROM users WHERE id = '01ARZ3NDEKTSV4RRFFQ69G5FAV';
Cast ulid to timestamp:
ALTER TABLE users ADD COLUMN created_at timestamp GENERATED ALWAYS AS (id::timestamp) STORED;
Cast timestamp to ulid, this generates a zeroed ULID with the timestamp prefixed (TTTTTTTTTT0000000000000000):
-- gets all users where the ID was created on 2023-09-15, without using another column and taking advantage of the index SELECT * FROM users WHERE id BETWEEN '2023-09-15'::timestamp::ulid AND '2023-09-16'::timestamp::ulid;
Use pgrx. You can clone this repo and install this extension locally by following this guide.
You can also download relevant installation packages from releases page.
If you encounter the exclusive lock error while using pgx_ulid, follow these steps to resolve the issue:
Alter the system to set shared_preload_libraries to pgx_ulid by running the following SQL command:
ALTER SYSTEM SET shared_preload_libraries = 'pgx_ulid';
Restart the PostgreSQL service to apply the changes. The command to restart PostgreSQL depends on your system.
Verify that ulid is successfully loaded into shared libraries by executing:
SHOW shared_preload_libraries;
Here is a list of Contributors
MIT/X11
Report here.
Pavan Kumar Sunkara (pavan.sss1991@gmail.com)